Glioblastoma mutliforme (GBM) is the most common form of primary brain cancer. Despite aggressive therapies including surgery, radiotherapy, and chemotherapy, recurrent disease is nearly always fatal. Oncolytic HSV vectors (e.g. G207) have shown some promise in the treatment of GBM however there have been few complete responses, a disappointing outcome most likely related to inadequate vector infection and growth, particularly among tumor cells that migrate from the tumor mass and invade normal brain tissue. Thus a central goal of Project 3 is to improve oncolytic vector delivery, replication and spread while maintaining safety and tumor specificity. Because changes in the tumor microenvironment greatly influence virus growth, we propose further to arm these oncolytic vectors with genes that improve vector distribution, overcome local anti-viral responses and enhance susceptibility to apoptotic mechanisms. Specifically, we propose to: (i) to explore the growth, spread and anti-tumor potential of a highly active HSV -1 strain KOS Oncolytic Vector (KOV) deleted for the non-essential immediate early (I.E.) genes ICPO, ICP22 and ICP47, (ii) to employ a recombinant KOV vector expressing a secreted matrix metalloproteinase protease (ADAMTS-8) with strong anti-angiogenic activity in an effort to increase initial vector distribution and to facilitate vector spread during replication, (iii) examine the use of a recombinant KOV capable of expressing VH1, binl and a dominant negative IKB (kBaM) as inhibitors of the interferon gamma (IFNy) and indoleamine 2,3-dioxygenase (IDO) antiviral and cytokine induction pathways and (iv) to evaluate the ability of recombinant KOV expressing (a) a novel dominant negative PKCe (DNP) that blocks its anti-apoptotic function, (b) caspase 8a to launch the apoptotic cascade and (c) an optimized recombinant soluble TRAIL (orsTRAIL) to induce tumor cell apoptosis. Ultimately, it is our intention to create a powerful oncolytic vector that exploits these combined growth-facilitating, anti-tumor functions that will set a new standard for this form of glioma therapy. This new vector will be compared to G207 to demonstrate improved anti-tumor responses. The highly engineered vector will also provide opportunities to better understand glioma cell biology, greatly improve the use of anti-cancer drugs in collaboration with Project 1 and assist the induction of tumor-specific immunity in collaboration with Project 2. Together our replication competent gene vectors should be useful in the development of an effective multi-modal therapy, an important overall goal of our program project grant.